Sn is widely used as a plating material for forming a coating film on the surface of a metal material. For example, as an electronic component material such as a lead frame and a connector, a plated copper material obtained by performing Sn plating or solder plating on the surface of a copper base material made of copper or a copper alloy has been widely used. The plated copper material is also used in the semiconductor device mentioned above.
In addition, a tinplate material in which a Sn coating is formed on a steel sheet has been hitherto used for various purposes.
Here, in a case of performing Sn plating, there is concern that the characteristics of a coating film may change due to precipitation of impurities in a plating solution together with Sn. Furthermore, impurities in the plating solution greatly affect the plating properties. Therefore, there is a demand for a plating solution with a reduced amount of impurities.
As a Sn supply material for supplying Sn to the plating solution mentioned above, powder of stannous oxide or the like is typically used. The stannous oxide powder is required to dissolve quickly in the plating solution and to have a reduced amount of impurities.
Here, Patent Documents 1 and 2 provide a stannous oxide powder which has a small amount of alkali and chlorine and is readily soluble in acid.